Control of engine torque for traction and stability control events for a hybrid powertrain system

ABSTRACT

An internal combustion engine is mechanically coupled to a hybrid transmission to transmit mechanical power to an output member. A method for controlling the internal combustion engine includes determining an accelerator output torque request based upon an operator input to the accelerator pedal, and determining an axle torque response type. A preferred input torque from the engine to the hybrid transmission is determined based upon the accelerator output torque request. An allowable range of input torque from the engine which can be reacted with the hybrid transmission is determined based upon the accelerator output torque request and the axle torque response type. The engine is controlled to meet the preferred input torque when the preferred input torque is within the allowable range of input torque from the engine. The engine is controlled within the allowable range of input torque from the engine when the preferred input torque is outside the allowable range of input torques from the engine.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60/985,256, filed on Nov. 4, 2007 which is hereby incorporated herein byreference.

TECHNICAL FIELD

This disclosure pertains to control systems for hybrid powertrainsystems.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

Known hybrid powertrain architectures can include multipletorque-generative devices, including internal combustion engines andnon-combustion machines, e.g., electric machines, which transmit torquethrough a transmission device to an output member. One exemplary hybridpowertrain includes a two-mode, compound-split, electro-mechanicaltransmission which utilizes an input member for receiving tractivetorque from a prime mover power source, preferably an internalcombustion engine, and an output member. The output member can beoperatively connected to a driveline for a motor vehicle fortransmitting tractive torque thereto. Machines, operative as motors orgenerators, can generate torque inputs to the transmission independentlyof a torque input from the internal combustion engine. The Machines maytransform vehicle kinetic energy transmitted through the vehicledriveline to energy that is storable in an energy storage device. Acontrol system monitors various inputs from the vehicle and the operatorand provides operational control of the hybrid powertrain, includingcontrolling transmission operating state and gear shifting, controllingthe torque-generative devices, and regulating the power interchangeamong the energy storage device and the machines to manage outputs ofthe transmission, including torque and rotational speed.

SUMMARY

An internal combustion engine is mechanically coupled to a hybridtransmission to transmit mechanical power to an output member. A methodfor controlling the internal combustion engine includes determining anaccelerator output torque request based upon an operator input to theaccelerator pedal, and determining an axle torque response type. Apreferred input torque from the engine to the hybrid transmission isdetermined based upon the accelerator output torque request. Anallowable range of input torque from the engine which can be reactedwith the hybrid transmission is determined based upon the acceleratoroutput torque request and the axle torque response type. The engine iscontrolled to meet the preferred input torque when the preferred inputtorque is within the allowable range of input torque from the engine.The engine is controlled within the allowable range of input torque fromthe engine when the preferred input torque is outside the allowablerange of input torques from the engine.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments will now be described, by way of example, withreference to the accompanying drawings, in which:

FIG. 1 is a schematic diagram of an exemplary hybrid powertrain, inaccordance with the present disclosure;

FIG. 2 is a schematic diagram of an exemplary architecture for a controlsystem and hybrid powertrain, in accordance with the present disclosure;

FIGS. 3 and 4 are schematic flow diagrams of a control scheme, inaccordance with the present disclosure; and

FIGS. 5 and 6 are graphical diagrams, in accordance with the presentdisclosure.

DETAILED DESCRIPTION

Referring now to the drawings, wherein the showings are for the purposeof illustrating certain exemplary embodiments only and not for thepurpose of limiting the same, FIGS. 1 and 2 depict an exemplary hybridpowertrain. The exemplary hybrid powertrain in accordance with thepresent disclosure is depicted in FIG. 1, comprising a two-mode,compound-split, electro-mechanical hybrid transmission 10 operativelyconnected to an engine 14 and torque machines comprising first andsecond electric machines (‘MG-A’) 56 and (‘MG-B’) 72. The engine 14 andthe torque machines, i.e., the first and second electric machines 56 and72 each generate power which can be transmitted to the transmission 10.The power generated by the engine 14 and the first and second electricmachines 56 and 72 and transmitted to the transmission 10 is describedin terms of input and motor torques, referred to herein as T_(I), T_(A),and T_(B) respectively, and speed, referred to herein as N_(I), N_(A),and N_(B), respectively.

The exemplary engine 14 comprises a multi-cylinder internal combustionengine selectively operative in several states to transmit torque to thetransmission 10 via an input shaft 12, and can be either aspark-ignition or a compression-ignition engine. The engine 14 includesa crankshaft (not shown) operatively coupled to the input shaft 12 ofthe transmission 10. A rotational speed sensor 11 monitors rotationalspeed of the input shaft 12. Power output from the engine 14, comprisingrotational speed and output torque, can differ from the input speedN_(I) and the input torque T_(I) to the transmission 10 due to placementof torque-consuming components on the input shaft 12 between the engine14 and the transmission 10, e.g., a hydraulic pump (not shown) and/or atorque management device (not shown).

The exemplary transmission 10 comprises three planetary-gear sets 24, 26and 28, and four selectively engageable torque-transmitting devices,i.e., clutches C1 70, C2 62, C3 73, and C4 75. As used herein, clutchesrefer to any type of friction torque transfer device including single orcompound plate clutches or packs, band clutches, and brakes, forexample. A hydraulic control circuit 42, preferably controlled by atransmission control module (hereafter ‘TCM’) 17, is operative tocontrol clutch states. Clutches C2 62 and C4 75 preferably comprisehydraulically-applied rotating friction clutches. Clutches C1 70 and C373 preferably comprise hydraulically-controlled stationary devices thatcan be selectively grounded to a transmission case 68. Each of theclutches C1 70, C2 62, C3 73, and C4 75 is preferably hydraulicallyapplied, selectively receiving pressurized hydraulic fluid via thehydraulic control circuit 42.

The first and second electric machines 56 and 72 preferably comprisethree-phase AC machines, each including a stator (not shown) and a rotor(not shown), and respective resolvers 80 and 82. The motor stator foreach machine is grounded to an outer portion of the transmission case68, and includes a stator core with coiled electrical windings extendingtherefrom. The rotor for the first electric machine 56 is supported on ahub plate gear that is operatively attached to shaft 60 via the secondplanetary gear set 26. The rotor for the second electric machine 72 isfixedly attached to a sleeve shaft hub 66.

Each of the resolvers 80 and 82 preferably comprises a variablereluctance device including a resolver stator (not shown) and a resolverrotor (not shown). The resolvers 80 and 82 are appropriately positionedand assembled on respective ones of the first and second electricmachines 56 and 72. Stators of respective ones of the resolvers 80 and82 are operatively connected to one of the stators for the first andsecond electric machines 56 and 72. The resolver rotors are operativelyconnected to the rotor for the corresponding first and second electricmachines 56 and 72. Each of the resolvers 80 and 82 is signally andoperatively connected to a transmission power inverter control module(hereafter ‘TPIM’) 19 and each senses and monitors rotational positionof the resolver rotor relative to the resolver stator, thus monitoringrotational position of respective ones of first and second electricmachines 56 and 72. Additionally, the signals output from the resolvers80 and 82 are interpreted to provide the rotational speeds for first andsecond electric machines 56 and 72, i.e., N_(A) and N_(B), respectively.

The transmission 10 includes an output member 64, e.g. a shaft, which isoperably connected to a driveline 90 for a vehicle (not shown), toprovide output power, e.g., to vehicle wheels 93, one of which is shownin FIG. 1. The output power is characterized in terms of an outputrotational speed N_(O) and an output torque T_(O). A transmission outputspeed sensor 84 monitors rotational speed and rotational direction ofthe output member 64. Each of the vehicle wheels 93 is preferablyequipped with a sensor 94 adapted to monitor wheel speed, the output ofwhich is monitored by a control module of a distributed control modulesystem described with respect to FIG. 2, to determine vehicle speed, andabsolute and relative wheel speeds for braking control, tractioncontrol, and vehicle acceleration management.

The input torque from the engine 14 and the motor torques from the firstand second electric machines 56 and 72 (T_(I), T_(A), and T_(B)respectively) are generated as a result of energy conversion from fuelor electrical potential stored in an electrical energy storage device(hereafter ‘ESD’) 74. The ESD 74 is high voltage DC-coupled to the TPIM19 via DC transfer conductors 27. The transfer conductors 27 include acontactor switch 38. When the contactor switch 38 is closed, undernormal operation, electric current can flow between the ESD 74 and theTPIM 19. When the contactor switch 38 is opened electric current flowbetween the ESD 74 and the TPIM 19 is interrupted. The TPIM 19 transmitselectrical power to and from the first electric machine 56 by transferconductors 29, and the TPIM 19 similarly transmits electrical power toand from the second electric machine 72 by transfer conductors 31, inresponse to torque commands for the first and second electric machines56 and 72 to meet the motor torques T_(A) and T_(B). Electrical currentis transmitted to and from the ESD 74 in accordance with whether the ESD74 is being charged or discharged.

The TPIM 19 includes the pair of power inverters (not shown) andrespective motor control modules (not shown) configured to receive thetorque commands and control inverter states therefrom for providingmotor drive or regeneration functionality to meet the commanded motortorques T_(A) and T_(B). The power inverters comprise knowncomplementary three-phase power electronics devices, and each includes aplurality of insulated gate bipolar transistors (not shown) forconverting DC power from the ESD 74 to AC power for powering respectiveones of the first and second electric machines 56 and 72, by switchingat high frequencies. The insulated gate bipolar transistors form aswitch mode power supply configured to receive control commands. Thereis typically one pair of insulated gate bipolar transistors for eachphase of each of the three-phase electric machines. States of theinsulated gate bipolar transistors are controlled to provide motor drivemechanical power generation or electric power regenerationfunctionality. The three-phase inverters receive or supply DC electricpower via DC transfer conductors 27 and transform it to or fromthree-phase AC power, which is conducted to or from the first and secondelectric machines 56 and 72 for operation as motors or generators viatransfer conductors 29 and 31 respectively.

FIG. 2 is a schematic block diagram of the distributed control modulesystem. The elements described hereinafter comprise a subset of anoverall vehicle control architecture, and provide coordinated systemcontrol of the exemplary hybrid powertrain described in FIG. 1. Thedistributed control module system synthesizes pertinent information andinputs, and executes algorithms to control various actuators to achievecontrol objectives, including objectives related to fuel economy,emissions, performance, drivability, and protection of hardware,including batteries of ESD 74 and the first and second electric machines56 and 72. The distributed control module system includes an enginecontrol module (hereafter ‘ECM’) 23, the TCM 17, a battery pack controlmodule (hereafter ‘BPCM’) 21, a brake control module (hereafter ‘BrCM’)22, and the TPIM 19. A hybrid control module (hereafter ‘HCP’) 5provides supervisory control and coordination of the ECM 23, the TCM 17,the BPCM 21, the BrCM 22 and the TPIM 19. A user interface (‘UI’) 13 isoperatively connected to a plurality of devices through which a vehicleoperator controls or directs operation of the electro-mechanical hybridpowertrain. The devices include an accelerator pedal 113 (‘AP’) fromwhich an operator torque request is determined, an operator brake pedal112 (‘BP’), a transmission gear selector 114 (‘PRNDL’), and a vehiclespeed cruise control (not shown). The transmission gear selector 114 mayhave a discrete number of operator-selectable positions, including therotational direction of the output member 64 to enable one of a forwardand a reverse direction.

The aforementioned control modules communicate with other controlmodules, sensors, and actuators via a local area network (hereafter‘LAN’) bus 6. The LAN bus 6 allows for structured communication ofstates of operating parameters and actuator command signals between thevarious control modules. The specific communication protocol utilized isapplication-specific. The LAN bus 6 and appropriate protocols providefor robust messaging and multi-control module interfacing between theaforementioned control modules, and other control modules providingfunctionality such as antilock braking, traction control, and vehiclestability. Multiple communications buses may be used to improvecommunications speed and provide some level of signal redundancy andintegrity. Communication between individual control modules can also beeffected using a direct link, e.g., a serial peripheral interface(‘SPI’) bus (not shown).

The HCP 5 provides supervisory control of the hybrid powertrain, servingto coordinate operation of the ECM 23, TCM 17, TPIM 19, and BPCM 21.Based upon various input signals from the user interface 13 and thehybrid powertrain, including the ESD 74, the HCP 5 determines variouscommands, including: the operator torque request, an output torquecommand (‘T_(CMD)’) to the driveline 90, an input torque command, clutchtorque(s) (‘T_(CL)’) for the applied torque-transfer clutches C1 70, C262, C3 73, C4 75 of the transmission 10; and the torque commands T_(A)and T_(B) for the first and second electric machines 56 and 72. The TCM17 is operatively connected to the hydraulic control circuit 42 andprovides various functions including monitoring various pressure sensingdevices (not shown) and generating and communicating control signals tovarious solenoids (not shown) thereby controlling pressure switches andcontrol valves contained within the hydraulic control circuit 42.

The ECM 23 is operatively connected to the engine 14, and functions toacquire data from sensors and control actuators of the engine 14 over aplurality of discrete lines, shown for simplicity as an aggregatebi-directional interface cable 35. The ECM 23 receives the input torquecommand from the HCP 5. The ECM 23 determines the actual input torque,T_(I), provided to the transmission 10 at that point in time based uponmonitored engine speed and load, which is communicated to the HCP 5. TheECM 23 monitors input from the rotational speed sensor 11 to determinethe engine input speed to the input shaft 12, which translates to thetransmission input speed, N_(I). The ECM 23 monitors inputs from sensors(not shown) to determine states of other engine operating parametersincluding, e.g., a manifold pressure, engine coolant temperature,ambient air temperature, and ambient pressure. The engine load can bedetermined, for example, from the manifold pressure, or alternatively,from monitoring operator input to the accelerator pedal 113. The ECM 23generates and communicates command signals to control engine actuators,including, e.g., fuel injectors, ignition modules, and throttle controlmodules, none of which are shown.

The TCM 17 is operatively connected to the transmission 10 and monitorsinputs from sensors (not shown) to determine states of transmissionoperating parameters. The TCM 17 generates and communicates commandsignals to control the transmission 10, including controlling thehydraulic control circuit 42. Inputs from the TCM 17 to the HCP 5include estimated clutch torques for each of the clutches, i.e., C1 70,C2 62, C3 73, and C4 75, and rotational output speed, N_(O), of theoutput member 64. Other actuators and sensors may be used to provideadditional information from the TCM 17 to the HCP 5 for controlpurposes. The TCM 17 monitors inputs from pressure switches (not shown)and selectively actuates pressure control solenoids (not shown) andshift solenoids (not shown) of the hydraulic control circuit 42 toselectively actuate the various clutches C1 70, C2 62, C3 73, and C4 75to achieve various transmission operating range states, as describedhereinbelow.

The BPCM 21 signally connects to sensors (not shown) to monitor the ESD74, including states of electrical current and voltage parameters, toprovide information indicative of parametric states of the batteries ofthe ESD 74 to the HCP 5. The parametric states of the batteriespreferably include battery state-of-charge, battery voltage, batterytemperature, and available battery power, referred to as a range P_(BAT)_(—) _(MIN) to P_(BAT) _(—) _(MAX).

The BrCM 22 is operatively connected to friction brakes (not shown) oneach of the vehicle wheels 93. The BrCM 22 monitors the operator inputto the brake pedal 112 and generates control signals to control thefriction brakes and sends a control signal to the HCP 5 to operate thefirst and second electric machines 56 and 72 based thereon.

Each of the control modules ECM 23, TCM 17, TPIM 19, BPCM 21, and BrCM22 is preferably a general-purpose digital computer comprising amicroprocessor or central processing unit, storage mediums comprisingread only memory (‘ROM’), random access memory (‘RAM’), electricallyprogrammable read only memory (‘EPROM’), a high speed clock, analog todigital (‘A/D’) and digital to analog (‘D/A’) circuitry, andinput/output circuitry and devices (‘I/O’) and appropriate signalconditioning and buffer circuitry. Each of the control modules has a setof control algorithms, comprising resident program instructions andcalibrations stored in one of the storage mediums and executed toprovide the respective functions of each computer. Information transferbetween the control modules is preferably accomplished using the LAN bus6 and SPI buses. The control algorithms are executed during preset loopcycles such that each algorithm is executed at least once each loopcycle. Algorithms stored in the non-volatile memory devices are executedby one of the central processing units to monitor inputs from thesensing devices and execute control and diagnostic routines to controloperation of the actuators, using preset calibrations. Loop cycles areexecuted at regular intervals, for example each 3.125, 6.25, 12.5, 25and 100 milliseconds during ongoing operation of the hybrid powertrain.Alternatively, algorithms may be executed in response to the occurrenceof an event.

The exemplary hybrid powertrain selectively operates in one of severaloperating range states that can be described in terms of an engine statecomprising one of an engine-on state (‘ON’) and an engine-off state(‘OFF’), and a transmission state comprising a plurality of fixed gearsand continuously variable operating modes, described with reference toTable 1, below.

TABLE 1 Engine Transmission Operating Applied Description State RangeState Clutches M1_Eng_Off OFF EVT Mode I C1 70 M1_Eng_On ON EVT Mode IC1 70 G1 ON Fixed Gear Ratio 1 C1 70 C4 75 G2 ON Fixed Gear Ratio 2 C170 C2 62 M2_Eng_Off OFF EVT Mode 2 C2 62 M2_Eng_On ON EVT Mode 2 C2 62G3 ON Fixed Gear Ratio 3 C2 62 C4 75 G4 ON Fixed Gear Ratio 4 C2 62 C373

Each of the transmission operating range states is described in thetable and indicates which of the specific clutches C1 70, C2 62, C3 73,and C4 75 are applied for each of the operating range states. A firstcontinuously variable mode, i.e., EVT Mode 1, or M1, is selected byapplying clutch C1 70 only in order to “ground” the outer gear member ofthe third planetary gear set 28. The engine state can be one of ON(‘M1_Eng_On’) or OFF (‘M1_Eng_Off’). A second continuously variablemode, i.e., EVT Mode 2, or M2, is selected by applying clutch C2 62 onlyto connect the shaft 60 to the carrier of the third planetary gear set28. The engine state can be one of ON (‘M2_Eng_On’) or OFF(‘M2_Eng_Off’). For purposes of this description, when the engine stateis OFF, the engine input speed is equal to zero revolutions per minute(‘RPM’), i.e., the engine crankshaft is not rotating. A fixed gearoperation provides a fixed ratio operation of input-to-output speed ofthe transmission 10, i.e., N_(I)/N_(O). A first fixed gear operation(‘G1’) is selected by applying clutches C1 70 and C4 75. A second fixedgear operation (‘G2’) is selected by applying clutches C1 70 and C2 62.A third fixed gear operation (‘G3’) is selected by applying clutches C262 and C4 75. A fourth fixed gear operation (‘G4’) is selected byapplying clutches C2 62 and C3 73. The fixed ratio operation ofinput-to-output speed increases with increased fixed gear operation dueto decreased gear ratios in the planetary gears 24, 26, and 28. Therotational speeds of the first and second electric machines 56 and 72,N_(A) and N_(B) respectively, are dependent on internal rotation of themechanism as defined by the clutching and are proportional to the inputspeed measured at the input shaft 12.

In response to operator input via the accelerator pedal 113 and brakepedal 112 as captured by the user interface 13, the HCP 5 and one ormore of the other control modules determine torque commands to controlthe torque actuators to meet the operator torque request at the outputmember 64 for transference to the driveline 90. The torque actuatorspreferably include torque generative devices, e.g., the engine 14 andtorque machines comprising the first and second electric machines 56 and72 in this embodiment. The torque actuators preferably further include atorque transferring device, comprising the transmission 10 in thisembodiment. Based upon input signals from the user interface 13 and thehybrid powertrain including the ESD 74, the HCP 5 determines theoperator torque request, a commanded output torque from the transmission10 to the driveline 90, an input torque from the engine 14, clutchtorques for the torque-transfer clutches C1 70, C2 62, C3 73, C4 75 ofthe transmission 10; and the motor torques for the first and secondelectric machines 56 and 72, respectively, as is described hereinbelow.

Final vehicle acceleration can be affected by other factors including,e.g., road load, road grade, and vehicle mass. The operating range stateis determined for the transmission 10 based upon a variety of operatingcharacteristics of the hybrid powertrain. This includes the operatortorque request, communicated through the accelerator pedal 113 and brakepedal 112 to the user interface 13 as previously described. Theoperating range state may be predicated on a hybrid powertrain torquedemand caused by a command to operate the first and second electricmachines 56 and 72 in an electrical energy generating mode or in atorque generating mode. The operating range state can be determined byan optimization algorithm or routine which determines optimum systemefficiency based upon operator demand for power, battery state ofcharge, and energy efficiencies of the engine 14 and the first andsecond electric machines 56 and 72. The control system manages torqueinputs from the engine 14 and the first and second electric machines 56and 72 based upon an outcome of the executed optimization routine, andsystem efficiencies are optimized thereby, to manage fuel economy andbattery charging. Furthermore, operation can be determined based upon afault in a component or system. The HCP 5 monitors the torque-generativedevices, and determines the power output from the transmission 10required in response to the desired output torque at output member 64 tomeet the operator torque request. As should be apparent from thedescription above, the ESD 74 and the first and second electric machines56 and 72 are electrically-operatively coupled for power flowtherebetween. Furthermore, the engine 14, the first and second electricmachines 56 and 72, and the electro-mechanical transmission 10 aremechanically-operatively coupled to transfer power therebetween togenerate a power flow to the output member 64.

FIG. 3 shows a control system architecture for controlling and managingsignals related to torque and power flow in a hybrid powertrain systemhaving multiple torque generative devices, described hereinbelow withreference to the hybrid powertrain system of FIGS. 1 and 2, and residingin the aforementioned control modules in the form of executablealgorithms and calibrations. The control system architecture isapplicable to alternative hybrid powertrain systems having multipletorque generative devices, including, e.g., a hybrid powertrain systemhaving a single electric machine, and a hybrid powertrain system havingmultiple electric machines. The control system architecture includes aplurality of inputs to a strategic optimization control scheme(‘Strategic Control’) 310, which determines a preferred input speed(‘Ni_Des’) and a preferred operating range state (‘Hybrid Range StateDes’) based upon the output speed and the operator torque request, andoptimized based upon other operating parameters of the hybridpowertrain, including battery power limits and response limits of theengine 14, transmission 10, and first and second electric machines 56and 72. The strategic optimization control scheme 310 is preferablyexecuted by the HCP 5 during each 100 ms loop cycle and each 25 ms loopcycle.

The outputs of the strategic optimization control scheme 310 are used ina shift execution and engine start/stop control scheme (‘Shift Executionand Engine Start/Stop’) 320 to command changes in the transmissionoperation (‘Transmission Commands’) including changing the operatingrange state. This includes commanding execution of a change in theoperating range state if the preferred operating range state isdifferent from the present operating range state by commanding changesin application of one or more of the clutches C1 70, C2 62, C3 73, andC4 75 and other transmission commands. The present operating range state(‘Hybrid Range State Actual’) and an input speed profile (‘Ni_Prof’) canbe determined. The input speed profile is an estimate of an upcomingtime-rate change in the input speed and preferably comprises a scalarparametric value that is a targeted input speed for the forthcoming loopcycle, based upon the engine operating commands and the operator torquerequest during a transition in the operating range state of thetransmission.

A tactical control scheme (‘Tactical Control and Operation’) 330 isrepeatedly executed during one of the control loop cycles to determineengine commands (‘Engine Commands’) for operating the engine 14,including a preferred input torque from the engine 14 to thetransmission 10 based upon the output speed, the input speed, and theoperator torque request comprising the immediate accelerator outputtorque request, the predicted accelerator output torque request, theimmediate brake output torque request, the predicted brake output torquerequest, the axle torque response type, and the present operating rangestate for the transmission. The engine commands also include enginestates including one of an all-cylinder operating state and a cylinderdeactivation operating state wherein a portion of the engine cylindersare deactivated and unfueled, and engine states including one of afueled state and a fuel cutoff state. An engine command comprising thepreferred input torque of the engine 14 and a present input torque(‘Ti’) reacting between the engine 14 and the input member 12 arepreferably determined in the ECM 23. Clutch torques (‘Tcl’) for each ofthe clutches C1 70, C2 62, C3 73, and C4 75, including the presentlyapplied clutches and the non-applied clutches are estimated, preferablyin the TCM 17.

An output and motor torque determination scheme (‘Output and MotorTorque Determination’) 340 is executed to determine the preferred outputtorque from the powertrain (‘To_cmd’). This includes determining motortorque commands (‘T_(A)’, ‘T_(B)’) to transfer a net commanded outputtorque to the output member 64 of the transmission 10 that meets theoperator torque request, by controlling the first and second electricmachines 56 and 72 in this embodiment. The immediate accelerator outputtorque request, the immediate brake output torque request, the presentinput torque from the engine 14 and the estimated applied clutchtorque(s), the present operating range state of the transmission 10, theinput speed, the input speed profile, and the axle torque response typeare inputs. The output and motor torque determination scheme 340executes to determine the motor torque commands during each iteration ofone of the loop cycles. The output and motor torque determination scheme340 includes algorithmic code which is regularly executed during the6.25 ms and 12.5 ms loop cycles to determine the preferred motor torquecommands.

The hybrid powertrain is controlled to transfer the output torque to theoutput member 64 to react with the driveline 90 to generate tractivetorque at wheel(s) 93 to forwardly propel the vehicle in response to theoperator input to the accelerator pedal 113 when the operator selectedposition of the transmission gear selector 114 commands operation of thevehicle in the forward direction. Similarly, the hybrid powertrain iscontrolled to transfer the output torque to the output member 64 toreact with the driveline 90 to generate tractive torque at wheel(s) 93to propel the vehicle in a reverse direction in response to the operatorinput to the accelerator pedal 113 when the operator selected positionof the transmission gear selector 114 commands operation of the vehiclein the reverse direction. Preferably, propelling the vehicle results invehicle acceleration so long as the output torque is sufficient toovercome external loads on the vehicle, e.g., due to road grade,aerodynamic loads, and other loads.

Operating the powertrain system includes shifting transmission operationbetween operating range states, which can include transitioning to oneor more intermediate operating range states during a shift andcontrolling engine operation to achieve target input speeds. Capabilityto change operation of the engine 14 from a present speed to the targetinput speed can include executing algorithms to determine an achievableor preferred input member acceleration rate, e.g., one of the preferredacceleration rates comprising an immediate lead input accelerationprofile and a predicted lead input acceleration profile. This includesselecting independently controllable parameters for controlling thetransfer of power through the powertrain system. Parametric equationsare derived for the acceleration rate of the input member based upontorque outputs from the first and second torque machines, e.g., thefirst and second electric machines 56 and 72 in one embodiment. Thealgorithms are executed to simultaneously solve the parametric equationsand determine a preferred acceleration rate for the input member.Operation of the engine 14 can be controlled to achieve the preferredacceleration rate for the input member 12.

The BrCM 22 commands the friction brakes on the wheels 93 to applybraking force and generates a command for the transmission 10 to createa negative output torque which reacts with the driveline 90 in responseto a net operator input to the brake pedal 112 and the accelerator pedal113. Preferably the applied braking force and the negative output torquecan decelerate and stop the vehicle so long as they are sufficient toovercome vehicle kinetic power at wheel(s) 93. The negative outputtorque reacts with the driveline 90, thus transferring torque to theelectro-mechanical transmission 10 and the engine 14. The negativeoutput torque reacted through the electro-mechanical transmission 10 canbe transferred to the first and second electric machines 56 and 72 togenerate electric power for storage in the ESD 74.

The operator inputs to the accelerator pedal 113 and the brake pedal 112comprise individually determinable operator torque request inputsincluding an immediate accelerator output torque request (‘Output TorqueRequest Accel Immed’), a predicted accelerator output torque request(‘Output Torque Request Accel Prdtd’), an immediate brake output torquerequest (‘Output Torque Request Brake Immed’), a predicted brake outputtorque request (‘Output Torque Request Brake Prdtd’) and the axle torqueresponse type (‘Axle Torque Response Type’). As used herein, the term‘accelerator’ refers to an operator request for forward propulsionpreferably resulting in increasing vehicle speed over the presentvehicle speed, when the operator selected position of the transmissiongear selector 114 commands operation of the vehicle in the forwarddirection. The terms ‘deceleration’ and ‘brake’ refer to an operatorrequest preferably resulting in decreasing vehicle speed from thepresent vehicle speed. The immediate accelerator output torque request,the predicted accelerator output torque request, the immediate brakeoutput torque request, the predicted brake output torque request, andthe axle torque response type are individual inputs to the controlsystem including to the tactical control scheme 330.

The immediate accelerator output torque request is determined based upona presently occurring operator input to the accelerator pedal 113, andcomprises a request to generate an immediate output torque at the outputmember 64 preferably to accelerate the vehicle. The immediateaccelerator output torque request is unshaped, but can be shaped byevents that affect vehicle operation outside the powertrain control.Such events include vehicle level interruptions in the powertraincontrol for antilock braking, traction control and vehicle stabilitycontrol, which can be used to shape or rate-limit the immediateaccelerator output torque request.

The predicted accelerator output torque request is determined based uponthe operator input to the accelerator pedal 113 and comprises an optimumor preferred output torque at the output member 64. The predictedaccelerator output torque request is preferably equal to the immediateaccelerator output torque request during normal operating conditions,e.g., when any one of antilock braking, traction control, or vehiclestability is not being commanded. When any one of antilock braking,traction control or vehicle stability is being commanded the predictedaccelerator output torque request remains the preferred output torquewith the immediate accelerator output torque request being decreased inresponse to output torque commands related to the antilock braking,traction control, or vehicle stability control.

Blended brake torque includes a combination of the friction brakingtorque generated at the wheels 93 and the output torque generated at theoutput member 64 which reacts with the driveline 90 to decelerate thevehicle in response to the operator input to the brake pedal 112.

The immediate brake output torque request is determined based upon apresently occurring operator input to the brake pedal 112, and comprisesa request to generate an immediate output torque at the output member 64to effect a reactive torque with the driveline 90 which preferablydecelerates the vehicle. The immediate brake output torque request isdetermined based upon the operator input to the brake pedal 112 and thecontrol signal to control the friction brakes to generate frictionbraking torque.

The predicted brake output torque request comprises an optimum orpreferred brake output torque at the output member 64 in response to anoperator input to the brake pedal 112 subject to a maximum brake outputtorque generated at the output member 64 allowable regardless of theoperator input to the brake pedal 112. In one embodiment the maximumbrake output torque generated at the output member 64 is limited to −0.2g. The predicted brake output torque request can be phased out to zerowhen vehicle speed approaches zero regardless of the operator input tothe brake pedal 112. As desired by a user, there can be operatingconditions under which the predicted brake output torque request is setto zero, e.g., when the operator setting to the transmission gearselector 114 is set to a reverse gear, and when a transfer case (notshown) is set to a four-wheel drive low range. The operating conditionswhereat the predicted brake output torque request is set to zero arethose in which blended braking is not preferred due to vehicle operatingfactors.

The axle torque response type comprises an input state for shaping andrate-limiting the output torque response through the first and secondelectric machines 56 and 72. The input state for the axle torqueresponse type can be an active state, preferably comprising one of apleasability limited state a maximum range state, and an inactive state.When the commanded axle torque response type is the active state, theoutput torque command is the immediate output torque. Preferably thetorque response for this response type is as fast as possible.

The predicted accelerator output torque request and the predicted brakeoutput torque request are input to the strategic optimization controlscheme (‘Strategic Control’) 310. The strategic optimization controlscheme 310 determines a desired operating range state for thetransmission 10 (‘Hybrid Range State Des’) and a desired input speedfrom the engine 14 to the transmission 10 (‘Ni Des’), which compriseinputs to the shift execution and engine operating state control scheme(‘Shift Execution and Engine Start/Stop’) 320.

A change in the input torque from the engine 14 which reacts with theinput member from the transmission 10 can be effected by changing massof intake air to the engine 14 by controlling position of an enginethrottle utilizing an electronic throttle control system (not shown),including opening the engine throttle to increase engine torque andclosing the engine throttle to decrease engine torque. Changes in theinput torque from the engine 14 can be effected by adjusting ignitiontiming, including retarding spark timing from a mean-best-torque sparktiming to decrease engine torque. The engine state can be changedbetween the engine-off state and the engine-on state to effect a changein the input torque. The engine state can be changed between theall-cylinder operating state and the cylinder deactivation operatingstate, wherein a portion of the engine cylinders are unfueled. Theengine state can be changed by selectively operating the engine 14 inone of the fueled state and the fuel cutoff state wherein the engine isrotating and unfueled. Executing a shift in the transmission 10 from afirst operating range state to a second operating range state can becommanded and achieved by selectively applying and deactivating theclutches C1 70, C2 62, C3 73, and C4 75.

FIG. 4 details the tactical control scheme (‘Tactical Control andOperation’) 330 for controlling operation of the engine 14, describedwith reference to the hybrid powertrain system of FIGS. 1 and 2 and thecontrol system architecture of FIG. 3. The tactical control scheme 330includes a tactical optimization control path 350 and a systemconstraints control path 360 which are preferably executed concurrently.The outputs of the tactical optimization control path 350 are input toan engine state control scheme 370. The outputs of the engine statecontrol scheme 370 and the system constraints control path 360 are inputto an engine response type determination scheme (‘Engine Response TypeDetermination’) 380 for controlling the engine state, the immediateengine torque request and the predicted engine torque request.

The operating point of the engine 14 as described in terms of the inputtorque and input speed that can be achieved by controlling mass ofintake air to the engine 14 when the engine 14 comprises aspark-ignition engine by controlling position of an engine throttle (notshown) utilizing an electronic throttle control device (not shown). Thisincludes opening the throttle to increase the engine input speed andtorque output and closing the throttle to decrease the engine inputspeed and torque. The engine operating point can be achieved byadjusting ignition timing, generally by retarding spark timing from amean-best-torque spark timing to decrease engine torque.

When the engine 14 comprises a compression-ignition engine, theoperating point of the engine 14 can be achieved by controlling the massof injected fuel, and adjusted by retarding injection timing from amean-best-torque injection timing to decrease engine torque.

The engine operating point can be achieved by changing the engine statebetween the engine-off state and the engine-on state. The engineoperating point can be achieved by controlling the engine state betweenthe all-cylinder state and the cylinder deactivation state, wherein aportion of the engine cylinders are unfueled and the engine valves aredeactivated. The engine state can include the fuel cutoff state whereinthe engine is rotating and unfueled to effect engine braking.

The tactical optimization control path 350 acts on substantially steadystate inputs to select a preferred engine state and determine apreferred input torque from the engine 14 to the transmission 10. Theinputs originate in the shift execution and engine operating statecontrol scheme 320. The tactical optimization control path 350 includesan optimization scheme (‘Tactical Optimization’) 354 to determinepreferred input torques for operating the engine 14 in the all-cylinderstate (‘Input Torque Full’), in the cylinder deactivation state (‘InputTorque Deac’), the all-cylinder state with fuel cutoff (‘Input TorqueFull FCO’), in the cylinder deactivation state with fuel cutoff (‘InputTorque Deac FCO’), and a preferred engine state (‘Preferred EngineState’). Inputs to the optimization scheme 354 include a lead operatingrange state of the transmission 10 (‘Lead Hybrid Range State’) apredicted lead input acceleration profile (‘Lead Input AccelerationProfile Predicted’), a predicted range of clutch reactive torques(‘Predicted Clutch Reactive Torque Min/Max’) for each presently appliedclutch, predicted battery power limits (‘Predicted Battery PowerLimits’) and predicted output torque requests for acceleration (‘OutputTorque Request Accel Prdtd’) and braking (‘Output Torque Request BrakePrdtd’). The predicted output torque requests for acceleration andbraking are combined and shaped with the axle torque response typethrough a predicted output torque shaping filter 352 to yield apredicted net output torque request (‘To Net Prdtd’) and a predictedaccelerator output torque request (‘To Accel Prdtd’), which are inputsto the optimization scheme 354. The lead operating range state of thetransmission 10 comprises a time-shifted lead of the operating rangestate of the transmission 10 to accommodate a response time lag betweena commanded change in the operating range state and a measured change inthe operating range state. The predicted lead input acceleration profilecomprises a time-shifted lead of the predicted input accelerationprofile of the input member 12 to accommodate a response time lagbetween a commanded change in the predicted input acceleration profileand a measured change in the predicted input acceleration profile. Theoptimization scheme 354 determines costs for operating the engine 14 inthe engine states, which comprise operating the engine fueled and in theall-cylinder state (‘P_(COST FULL FUEL)’), operating the engine unfueledand in the all-cylinder state (‘P_(COST FULL FCO)’), operating theengine fueled and in cylinder deactivation state (‘P_(COST DEAC FUEL)’),and operating the engine unfueled and in the cylinder deactivation state(‘P_(COST DEAC FCO)’). The aforementioned costs for operating the engine14 are input to a stabilization analysis scheme (‘Stabilization andArbitration’) 356 along with the actual engine state (‘Actual EngineState’) and an allowable or permissible engine state (‘Engine StateAllowed’) to select one of the engine states as the preferred enginestate (‘Preferred Engine State’).

The preferred input torques for operating the engine 14 in theall-cylinder state and in the cylinder deactivation state with andwithout fuel cutoff are input to an engine torque conversion calculator(‘Engine Torque Conversion’) 355 and converted to preferred enginetorques in the all-cylinder state and in the cylinder deactivation state(‘Engine Torque Full’) and (‘Engine Torque Deac’) and with fuel cutoffin the all-cylinder state and in the cylinder deactivation state(‘Engine Torque Full FCO’) and (‘Engine Torque Deac FCO’) respectively,by taking into account parasitic and other loads introduced between theengine 14 and the transmission 10. The preferred engine torques foroperation in the all-cylinder state and in the cylinder deactivationstate and the preferred engine state comprise inputs to the engine statecontrol scheme 370.

The costs for operating the engine 14 include operating costs which aregenerally determined based upon factors that include vehicledriveability, fuel economy, emissions, and battery usage. Costs areassigned and associated with fuel and electrical power consumption andare associated with a specific operating points of the hybridpowertrain. Lower operating costs are generally associated with lowerfuel consumption at high conversion efficiencies, lower battery powerusage, and lower emissions for each engine speed/load operating point,and take into account the present operating state of the engine 14.

The preferred engine state and the preferred engine torques in theall-cylinder state and in the cylinder deactivation state are input tothe engine state control scheme 370, which includes an engine statemachine (‘Engine State Machine’) 372. The engine state machine 372determines a target engine torque (‘Target Engine Torque’) and a targetengine state (‘Target Engine State’) based upon the preferred enginetorques and the preferred engine state. The target engine torque and thetarget engine state are input to a transition filter (‘TransitionFiltering’) 374 which monitors any commanded transition in the enginestate and filters the target engine torque to provide a filtered targetengine torque (‘Filtered Target Engine Torque’). The engine statemachine 372 outputs a command that indicates selection of one of thecylinder deactivation state and the all-cylinder state (‘DEAC Selected’)and indicates selection of one of the engine-on state and thedeceleration fuel cutoff state (‘FCO Selected’).

The selection of one of the cylinder deactivation state and theall-cylinder state and the selection of one of the engine-on state andthe deceleration fuel cutoff state, the filtered target engine torque,and the minimum and maximum engine torques are input to the engineresponse type determination scheme 380.

The system constraints control path 360 determines constraints on theinput torque, comprising minimum and maximum input torques (‘InputTorque Hybrid Minimum’ and ‘Input Torque Hybrid Maximum’) that can bereacted by the transmission 10. The minimum and maximum input torquesare determined based upon constraints to the transmission 10 and thefirst and second electric machines 56 and 72, including clutch torquesand battery power limits, which affect the capacity of the transmission10 to react input torque during the current loop cycle. Inputs to thesystem constraints control path 360 include the immediate output torquerequest as measured by the accelerator pedal 113 (‘Output Torque RequestAccel Immed’) and the immediate output torque request as measured by thebrake pedal 112 (‘Output Torque Request Brake Immed’) which are combinedand shaped with the axle torque response type through an immediateoutput torque shaping filter (‘Immediate Output Torque Shaping’) 362 toyield a net immediate output torque (‘To Net Immed’) and an immediateaccelerator output torque (‘To Accel Immed’). The net immediate outputtorque and the immediate accelerator output torque are inputs to aconstraints scheme (‘Output and Input Torque Constraints’) 364. Otherinputs to the constraints scheme 364 include the lead operating rangestate of the transmission 10, an immediate lead input accelerationprofile (‘Lead Input Acceleration Profile Immed’), a lead immediateclutch reactive torque range (‘Lead Immediate Clutch Reactive TorqueMin/Max’) for each presently applied clutch, and the available batterypower (‘Battery Power Limits’) comprising the range P_(BAT) _(—) _(MIN)to P_(BAT) _(—) _(MAX). The immediate lead input acceleration profilecomprises a time-shifted lead of the immediate input accelerationprofile of the input member 12 to accommodate a response time lagbetween a commanded change in the immediate input acceleration profileand a measured change in the immediate input acceleration profile. Thelead immediate clutch reactive torque range comprises a time-shiftedlead of the immediate clutch reactive torque range of the clutches toaccommodate a response time lag between a commanded change in theimmediate clutch torque range and a measured change in the immediateclutch reactive torque range. The constraints scheme 364 determines anoutput torque range for the transmission 10, and then determines theminimum and maximum allowable input torques (‘Input Torque HybridMinimum’ and ‘Input Torque Hybrid Maximum’ respectively) that can bereacted by the transmission 10 based upon the aforementioned inputs. Theminimum and maximum allowable input torques can change during ongoingoperation, due to changes in the aforementioned inputs, includingincreasing energy recovery through electric power regeneration throughthe transmission 14 and first and second electric machines 56 and 72.

The minimum and maximum allowable input torques are input to the enginetorque conversion calculator 355 and converted to minimum and maximumengine torques (‘Engine Torque Hybrid Minimum’ and ‘Engine Torque HybridMaximum’ respectively), by taking into account parasitic and other loadsintroduced between the engine 14 and the transmission 10.

The filtered target engine torque, the output of the engine statemachine 372 and the minimum and maximum engine torques are input to theengine response type determination scheme 380, which inputs the enginecommands to the ECM 23 for controlling the engine state, the immediateengine torque request and the predicted engine torque request. Theengine commands include an immediate engine torque request (‘EngineTorque Request Immed’) and a predicted engine torque request (‘EngineTorque Request Prdtd’) that can be determined based upon the filteredtarget engine torque. Other commands control the engine state to one ofthe engine fueled state and the deceleration fuel cutoff state (‘FCORequest’) and to one of the cylinder deactivation state and theall-cylinder state (‘DEAC Request’). Another output comprises an engineresponse type (‘Engine Response Type’). When the filtered target enginetorque is within the range between the minimum and maximum enginetorques, the engine response type is inactive. When the filtered targetengine torque is outside the constraints of the minimum and maximumengine torques (‘Engine Torque Hybrid Minimum’) and (‘Engine TorqueHybrid Maximum’) the engine response type is active, indicating a needfor an immediate change in the engine torque, e.g., through engine sparkcontrol and retard to change the engine torque and the input torque tofall within the constraints of the minimum and maximum engine torques.

FIGS. 5 and 6 graphically show operation of a method to control enginetorque input to a hybrid transmission, described with reference to theexemplary powertrain system described with reference to FIGS. 1 and 2utilizing a control system described with reference to FIGS. 3 and 4. Askilled practitioner can apply the method to other powertrain systems.

FIG. 5 shows operation of the powertrain including an event that causesthe control system to command an immediate reduction in the outputtorque at the output member 64 to the driveline 90, preferably by achange in the axle torque response type from the inactive state to theactive state that can be caused by a traction control event or a vehiclestability event. This causes the immediate accelerator output torquerequest (‘Output Torque Request Accel Immed’) to decrease. The systemconstraints control path 360 reduces the maximum engine torque that canbe reacted by the transmission 10 (‘Engine Torque Hybrid Maximum’). Whenthe maximum engine torque that can be reacted by the transmission 10becomes less than the preferred engine torque (‘Preferred EngineTorque’) for operating the engine 14 that is output from the tacticaloptimization control path 350, shown as point A, the engine responsetype output from the engine response type determination scheme 380changes the engine response type from inactive to active. The immediateengine torque request output (‘Engine Torque Request Immed’) decreasesconsistent with the maximum engine torque that can be reacted by thetransmission 10, and can be achieved by active engine management schemesincluding retarding spark advance, or advancing fuel injection timing toreduce the engine torque. This operation continues during the periodwhen the maximum engine torque that can be reacted by the transmission10 is less than the preferred engine torque for operating the engine 14.When the maximum engine torque that can be reacted by the transmission10 is greater than the preferred engine torque for operating the engine14, shown at point B, the engine response type shifts to inactive andengine operation discontinues the active engine management schemes.Subsequently the axle torque response type can become inactive. When theaxle torque response type changes from the active state to the inactivestate, the immediate and predicted output torque requests become equalwith the preferred engine torque for operating the engine 14.

FIG. 6 shows a second operation of the powertrain wherein an eventcauses the control system to command an immediate reduction in theoutput torque at the output member 64 to the driveline 90, preferably bya change in the axle torque response type from the inactive state to theactive state which can be caused by a traction control event or avehicle stability event. The immediate accelerator output torque request(‘Output Torque Request Accel Immed’) decreases. The system constraintscontrol path 360 reduces the maximum engine torque (‘Engine TorqueHybrid Maximum’) that can be reacted by the transmission 10. When themaximum engine torque that can be reacted by the transmission 10 remainsgreater than the preferred engine torque (‘Preferred Engine Torque’) foroperating the engine 14 that is output from the tactical optimizationcontrol path 350, the engine response type output from the engineresponse type determination scheme 380 remains as the immediate enginetorque request, and the engine operation is unaffected. The outputtorque from the powertrain system is reduced through control of theoutput and motor torque control scheme 340, and engine power can beconsumed by one of the electric machines, preferably to generateelectric power.

The method and system are described hereinabove with reference to anembodiment including the engine 14 and the first and second electricmachines 56 and 72 mechanically connected to the electro-mechanicaltransmission 10. Alternatively, the system can be used with otherelectro-mechanical transmission systems (not shown) which have a singleelectric machine. Alternatively, the system can be used with otherelectro-mechanical transmission systems (not shown) which have three ormore electric machines. Alternatively, the system can be used with otherhybrid transmission systems (not shown) which utilize torque-generativemachines and energy storage systems, e.g., hydraulic-mechanical hybridtransmissions.

It is understood that modifications are allowable within the scope ofthe disclosure. The disclosure has been described with specificreference to the preferred embodiments and modifications thereto.Further modifications and alterations may occur to others upon readingand understanding the specification. It is intended to include all suchmodifications and alterations insofar as they come within the scope ofthe disclosure.

1. Method for controlling an internal combustion engine mechanicallycoupled to a hybrid transmission to transfer power to a driveline,comprising: monitoring operator inputs to an accelerator pedal and abrake pedal; determining immediate and predicted accelerator outputtorque requests based upon the operator input to the accelerator pedal;determining an axle torque response type comprising one of active andinactive response; determining a preferred input torque from the engineto the hybrid transmission based upon the predicted accelerator outputtorque request; determining an allowable range of input torques from theengine to react with the hybrid transmission based upon the immediateaccelerator output torque request and the axle torque response type;operating the engine to meet the preferred input torque when thepreferred input torque is within the allowable range of input torquesfrom the engine; and operating the engine within the allowable range ofinput torques from the engine when the preferred input torque is outsidethe allowable range of input torques from the engine.
 2. The method ofclaim 1, comprising setting the axle torque response type to the activeresponse when one of a traction control event and a vehicle stabilityevent is commanded.
 3. The method of claim 1, wherein determining theimmediate accelerator output torque request based upon the operatorinput to the accelerator pedal comprises determining a presentlyoccurring operator input to the accelerator pedal to generate animmediate output torque.
 4. The method of claim 1, wherein determiningthe predicted accelerator torque request comprises a preferred outputtorque at the driveline.
 5. The method of claim 1, further comprisingincreasing the allowable range of input torques from the engine by powerregeneration through the hybrid transmission and operating the enginewithin the allowable range of input torques from the engine when thepreferred input torque is outside the allowable range of input torquesfrom the engine.
 6. The method of claim 1, further comprisingdetermining the allowable range of input torques from the engine whichcan be reacted with the hybrid transmission based upon power limits of asecond power generator operative to transfer mechanical power to thehybrid transmission and a torque transfer capacity of the hybridtransmission.
 7. The method of claim 1, further comprising operating theengine within the allowable range of input torques by decreasing thepower output from the engine.
 8. The method of claim 7, comprisingdecreasing the power output from the engine by retarding spark advanceof the engine.
 9. The method of claim 7, comprising decreasing the poweroutput from the engine by advancing timing of fuel injection of theengine.
 10. The method of claim 1, further comprising operating theengine within the allowable range of engine torque by increasing thepower output from the engine.
 11. Method for controlling an enginecoupled to a transmission device, the transmission device operative totransfer mechanical power from the engine and a second power generatingdevice to an output member, the method comprising: monitoring operatorinputs to an accelerator pedal and a brake pedal to determine animmediate accelerator torque request and a predicted accelerator outputtorque request; determining an axle torque response type comprising oneof active and inactive; determining a preferred input torque from theengine to the transmission device based upon the predicted acceleratoroutput torque request; determining an allowable range of input torquesfrom the engine which can be reacted by the transmission device basedupon the accelerator output torque request and the axle torque responsetype; operating the engine at the preferred input torque when thepreferred input torque is within the allowable range of input torquesfrom the engine which can be reacted by the transmission device; andoperating the engine within the allowable range of input torques fromthe engine when the preferred input torque is outside the allowablerange of input torques from the engine which can be reacted by thetransmission device.
 12. The method of claim 11, wherein the allowablerange of input torques from the engine which can be reacted by thetransmission device is determined based upon the predicted acceleratoroutput torque request when the axle torque response type is inactive.13. The method of claim 12, wherein the allowable range of input torquesfrom the engine which can be reacted by the transmission device isdetermined based upon the immediate accelerator output torque requestwhen the axle torque response type is active.
 14. The method of claim11, further comprising determining the allowable range of input torquesfrom the engine which can be reacted by the transmission device basedupon power limits of the second power generating device and a torquetransfer capacity of the transmission.
 15. The method of claim 14,further comprising including a selectively applied torque transferclutch in the transmission, and determining the torque transfer capacityof the transmission based upon a maximum reactive torque of theselectively applied clutch of the transmission.
 16. The method of claim11, wherein operating the engine within the allowable range of inputtorques from the engine comprises controlling spark advance of theengine to limit the torque output from the engine.
 17. The method ofclaim 11, wherein operating the engine within the allowable range ofinput torques from the engine comprises controlling timing of fuelinjection of the engine to limit the torque output from the engine. 18.Method for controlling an internal combustion engine mechanicallycoupled to a transmission device, the transmission device operative totransfer mechanical power between the engine and a second powergenerating device and an output member, the method comprising:monitoring operator inputs to an accelerator pedal and a brake pedal;determining an accelerator output torque request based upon the operatorinput to the accelerator pedal; determining an axle torque responsetype; determining a preferred input torque from the engine to thetransmission device based upon the accelerator output torque request;determining a maximum input torque from the engine which can be reactedwith the transmission device based upon the accelerator output torquerequest, the brake torque request and the axle torque response type;operating the engine at the preferred input torque when the preferredinput torque is less than the maximum input torque from the engine whichcan be reacted with the transmission device; and limiting the engine tooperate at the maximum input torque when the preferred input torque isgreater than the maximum input torque from the engine which can bereacted with the transmission device.